Just when you thought it was safe to venture outside again, another wide swath of bitter cold air began sweeping the nation Monday, thrusting temperatures to near zero degrees in the upper Midwest and promising to blast snow across parts of the Northeast.

It's not really the legendary "polar vortex" of Arctic air that smashed records across much of the nation two weeks ago, National Weather Service meteorologist Bob Oravec said. The polar vortex itself -- a strong area of low pressure that usually hugs the Arctic throughout the winter -- won't venture down over the U.S. But the cold air around it is coming -- and has no plans of leaving soon.

"It's already dipping below zero in parts of the upper Midwest, and temperatures there won't rise much over the next few days," Oravec said. He added that below-average temperatures -- even for some of the historically coldest days of the year -- will spread east and south.

Oravec said that while the last blast of mind-numbing cold air only stayed around for a couple days, this one could last a week or more as multiple cold fronts take turns dominating the weather pattern.

Walter Berg clears snow from his driveway on Jan. 18 in St. Cloud, Minn.(Photo: Dave Schwarz, The St. Cloud Times, via AP)

The highest temperature forecast for Detroit through Friday is 15 degrees. In Chicago, the high temperature could rise all the way to 28 degrees on Saturday -- but Sunday's forecast high drops back to 17.

The weather pattern will stretch into the Northeast on Tuesday. Washington, D.C., reached 58 degrees on Tuesday. Wednesday's forecast high: 18. And those low temperatures will be ushering in the snow Tuesday -- 3 to 7 inches for D.C.; 4 to 8 inches in New York City.

The snow will be stick around for a while in the sub-freezing temperatures, Oravec said. "It's going to be cold and windy for awhile and it's hitting an area of large population, so it will be a high impact event," he said.

The Southeast won't be spared. Atlanta and Birmingham, Ala., are among southern cities that could see lows dip into the teens this week.

All this weather excitement won't bring relief to parched areas of the West and Southwest, where Oravec said the forecast continues to be dry and warm.